Material, particularly elongated material, storage systems are known which include shelving units having vertical shelf supports with carrier arms secured thereon, one above another, so as to extend in the longitudinal direction, for carrying the magazines or pallet boxes. A crane is movable in the longitudinal direction and has carriages movable up and down along vertical guide means. Each carriage comprises a load fork with a vertical wall and a support bracket extending, in use, horizontally into the region of the store for engaging under legs protruding horizontally outwards from the ends of the magazines, in order to move the magazines within and between lanes separating the units.
Such material handling apparatus are disclosed, for example, in the referenced U.S. Pat. No. 4,778,325, and have a conveyor, movable on rails above the shelving units, from which load beams are vertically movably supported on carriages on both sides of the shelving units, the load beams moving, with guide means therefore, within the outline of the outer shelving unit supports. Load forks are horizontally movable in the storage space direction on the load beams. In this way, the load forks are vertically and horizontally mobile.
There is a need to ascertain the weight of each magazine taken up, as exactly as possible, in order to obtain an indication as to the degree to which the magazine is still filled, or whether perhaps a replenishment is necessary.
For this purpose, in the known apparatus, the conveyor portion mobile above the shelving units is divided into frame portions which are vertically supported one against the other through pressure cells. This form of construction, however, necessitates a relatively voluminous and expensive configuration for the conveyor. Moreover, it has the disadvantage that besides the weight of the magazine, the weight of the upper frame portion, which is supported on the lower frame of the conveyor via the pressure cells, and the weight of the load beams, the load forks and of the lifting means for moving the load beams is also weighed at the same time, so that the accuracy and fine sensitivity of the weighing apparatus are undesirably influenced.
Material handling apparatus in the form of gantry cranes are also known, for example, from U.S. Pat. No. 3,810,404. In this form of construction, it is not possible to provide weighing apparatus at a reasonable expense and, if a weighing apparatus were provided at all, it would involve an extraordinarily great loss of space.
Finally, material handling apparatus are known, such as these shown for example in German Patent DE-PS 35 03 390 C3, Dornieden, in which a gantry-type traveling crane is divided into two individual conveyor devices in the form of the initially mentioned vertical guide means which are mutually independently mobile but can be controlled synchronously.